OXFORD, Mississippi (CNN) - Iranian nuclear weapons would be an "existential threat to the state of Israel" and would encourage other countries in the Middle East to seek nuclear weapons as well, Sen. John McCain said Friday at his first presidential debate against Sen. Barack Obama.

"We cannot allow another Holocaust," he said.

Obama agreed that the United States "cannot tolerate a nuclear Iran," calling for tougher sanctions from a range of countries including Russia and China.

McCain called for a new "league of democracies" to stand firm against Iran.

He blasted Obama for being willing to meet "without preconditions" with Iranian President Mahmoud Ahmadinejad, who has repeated threatened Israel.

But Obama defended his stance, saying: "I reserve the right as president of the United States to meet with anyone at the time and place of my choosing if I think it's going to keep the American people safe."

OXFORD, Mississippi (CNN) - To me, this is the most difficult topic of all they have just gotten into: the deaths of American service people in Iraq. Essentially, it really boils down to this: If the U.S. pulls out before "victory," did they die for nothing?

McCain has never said those soldiers will have died in vain if there is not victory, but says that honoring them properly means not leaving before winning.

Obama says that no American soldier ever dies in vain. It is the most painful question, I think - something that will be discussed in the history books on this era.

OXFORD, Mississippi (CNN) - Iranian nuclear weapons would be an "existential threat to the state of Israel" and would encourage other countries in the Middle East to seek nuclear weapons as well, Sen. John McCain said Friday at his first presidential debate against Sen. Barack Obama.

There's a big disagreement between the candidates over what is the central front on the war on terror. Obama slams McCain on Afghanistan. McCain responds with a shot, that Obama has rarely visited Afghanistan.

OXFORD, Mississippi (CNN) - I think Jim Lehrer gave up trying to get them to talk to each other. It's even weirder in the hall - they are no more than 8 feet apart from each other and they speak to Lehrer only. But A+ for the effort.